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Light (or any radiation as a matter of fact) is an electromagnetic wave so why doesn't it have a electric charge associated with it? As far as I know only static or flowing electric chargers can produce electric fields and if it does have a charge why doesn't light (i.e. a photon) respond to an electric or magnetic field?

Qmechanic
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DUB
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  • Light has no charge. Being an electromagnetic wave is not connected to having a charge, and I do not understand why you would think it is. – ACuriousMind Sep 12 '14 at 15:54
  • Because electric fields don't exist on their own without a charge particle(s)? – DUB Sep 12 '14 at 15:58
  • Possible duplicate: http://physics.stackexchange.com/q/19632/2451 – Qmechanic Sep 12 '14 at 15:58
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    Why the downvotes? The question may look obvious to us nerds, but it wouldn't be obvious to non-physicists. Having said that, the question is a duplicate as Qmechanic suggests. – John Rennie Sep 12 '14 at 16:03
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    @JohnRennie: and it's even less trivial when you consider that the vector bosons in theories other than U(1) actually DO transform under the gauge transformation -- gluons have color, even if photons are uncharged, for example. – Zo the Relativist Sep 12 '14 at 16:10
  • @John Rennie: Yes, direct experiments to demonstrate the electric and the magnetic dipole were not successful. But it's possible to explain the birefringence by the way that the atomic distances of the crystal structure of some materials correspond with the photons wavelenght and the crystal has little bit different characteristics in two directions. The electric field of the randomly oriented photon will be oriented by the electric fields of the crystals electrons into this two directions and we see the double refraction. – HolgerFiedler Sep 12 '14 at 19:36

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You can think of light as the carrier of the electromagnetic interaction. The particles interact with light, not directly with each other. It is an experimental fact that light does not interact with itself.

Note that this is not the case with quantum chromodynamics (the theory of nuclear matter). This theory is built along the same lines as quantum electrodynamics (QED) but the gauge field is non abelian this time. The field is represented by matrices (instead of being a vector for QED) which do not commute with each other. This makes it necessary to consider field-field interactions. We get objects such as glueballs: bound states of field excitations only.

Steven Mathey
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  • I agree with all of this, but how does that explain why light shouldn't have an electric charge? Is your argument really that if they were charged, they wouldn't stick together to form bound states, or did I miss it? (this is not a jab, just asking for clarification.) – 299792458 Sep 12 '14 at 16:32
  • The answer to the question is in the first 3 sentences. The rest is just a side comment.The best answer that I can give is that it's an experimental fact. Nobody has ever measured anything else than zero for the charge of light. – Steven Mathey Sep 12 '14 at 17:22